Trailer wiring question - identify pins?
 

Quick question - I am about to remove some after-market trailer connection wiring and restore the "factory" loom as it has been cut up by a P.O.

Trailer lights all work fine but the CC announces "Check Trailer Lights" whenever a trailer is attached. I know why - and how to fix it but before I rip everything apart to restore the "factory" connections, I want to be sure about what the P.O.s modifications are doing. :confused:

On connector X393S, both pins 2 (GERT - Yellow and Red) and 5 (GRRT - Slate and Red) have been replaced by a high capacity +12v conductor wired to the battery positive via a large fused relay. This relay seems to be connected to the LCM up front (there's a single wire running to front of car) and to X393S pin 6 (SWWS - Black and White).

My question is; What signals are on X393S Pins 2, 5 and 6? I'm thinking the X393S pin 2 is the brake light circuit, and the others must something like reverse light and control. I guess I can stick a meter in each pin and watch for voltage jumps but if someone can decipher the pin outs for the TCM or connector X393S for me, I'd be very grateful! :thumbup:

FWIW, X393S pin 2 is labelled "55A", pin 5 is labelled "58AR" and pin 6 is labelled "53A". I have the E53 "hitch" PDF too but it doesn't tell me the circuit use - just everything else! :dunno:

Thanks in advance.

Well, I pulled the wiring last night - all good now - no issue with CC when the trailer is hooked up.

What I thought was a fused relay turned out to be just two 30A fuses - no relay. One feeding +12v directly from the battery to pin 2 on X393S and one feeding +12v to pin 5 on X393S but via a loop to somewhere up the front of the car, along with a wire tap from pin 6 on X393S. I have yet to determine what this part of the circuit is (was) doing, so I have yet to remove all the door sill trims and covers under the drivers foot well to determine what these wires are connected too. I think there may have been (still might be) a hidden switch up front somewhere and this circuit was to run aux .work lights or something. But I'm just guessing now!! :-)

I had to put two diodes in the trailer connector to tie the tail light circuit to the reverse lamp circuits - our trailers rarely have reverse lamps fitted and the CC expects to see them. Easy work around that seems to work well.

Speaking to myself at this point, but I'll add the final chapter for the sake of future searches.

Traced the wires running to front and as I kinda suspected, they terminated in an aftermarket connector (4-pin molex type) under the driver's foot well kick panel. Must have been a brake controller of some sort in there but it's gone now. The main thing is, I don't have any live wires floating about the car. I'll remove the wiring one day, if I ever pull the door sill trims and/or carpets; until then it can all stay there.

Used the trailer a couple of times, including taking it to it's bi-annual safety check, which it passed, including all electrical device operations. Phew!

End of story...